Many functions of modern devices in automotive, consumer and industrial applications such as converting electrical energy and driving an electric motor or an electric machine rely on semiconductor devices. It is often desirable that the semiconductor devices operate reliably with high slew rate, at low loss and with limiting the short circuit current e.g. at a failure of the load. To optimize device performance with respect to short circuit limitation and switching behavior, floating gates and floating semiconductor regions have been found to be useful in many applications. For example, a so called spaced-channel power IGBT (Insulated Gate Bipolar Transistor) has both a low on-voltage and a low switching loss so that the total loss is low. In a spaced-channel power IGBT, the channel regions (body regions) are spaced from each other by carrier storing floating regions. At least for reason of useful levels of the short circuit current, it is often desired to clamp the voltage fluctuations of the floating region in such devices. For gate electrodes and floating gate electrodes, a limitation of the voltage is often desirable e.g. for protecting the gate dielectric or for limiting short circuit current, respectively. For example, a power semiconductor device such as a power IGBT operating in a power converter or as a driver or switch of an electric motor may be exposed to high reverse currents and/or voltages during switching or an operating cycle. This may cause heavy voltage oscillations of the floating gate electrode and hence high stress for the gate dielectric. Accordingly, clamping circuits may be used to limit voltage fluctuations. For example, a pn-diode switched between the source or the gate driver and the floating semiconductor region and/or the floating gate may be used to limit the voltage fluctuations to the threshold voltage of the diode. Integrated diodes are often desirable to reduce handling requirements and to avoid additional inductivities. The integration of additional diodes is, however, often associated with increased processing requirements and costs.
For these and other reasons there is a need for the present invention.